Thus far, as medical devices at least part of which is brought into contact with or inserted into a subject such as a person, an endoscope system that observes the subject, an ultrasonic observation system including an ultrasonic endoscope system using ultrasonic waves, a treatment device system that applies energy to the subject, etc. have been commonly known. The medical device generally includes a patient circuit that is a circuit on the side of being brought into contact with or inserted into the subject and a ground-side circuit that is a circuit provided on the side of performing the transmission and reception of signals, the supply of electric power, etc. with the patient circuit and grounded by functional grounding, protective grounding for ensuring the safety of the manipulator of the medical device, or the like, such as the primary circuit and the secondary circuit. In such a medical device, electrical insulation is provided between the patient circuit and the ground-side circuit in order to ensure safety.
For the medical device, there is known a technology in which the reference potential of the patient circuit (the patient ground) and the reference potential of the ground-side circuit are connected by an impedance element such as a capacitor in an alternating current manner, and thereby the reference potential of the patient circuit is stabilized and the noise between the patient circuit and the ground-side circuit is reduced (e.g. see Patent Literature 1).